Vehicles having four-wheel drive capability that are designed for on-road and off-road use typically provide optional engagement/disengagement of two of the four wheels. Whereas the wheels to be disengaged are necessarily provided with a drive line from the transfer case to the wheels (a propeller shaft between the transfer case and differential and axles between the differential and the wheels), for on-road use and to avoid unnecessary energy consumption and wearing of the out of service drive line components, a first disconnect system disconnects the propeller shaft from the transfer case and a second disconnect system disconnects the axles from the wheels. This latter disconnect system is the hub lock device of the present invention.
The original hub lock devices were manually actuated. A driver/operator would stop the vehicle, engage the transfer case disconnect system and then manually turn a dial located in each wheel hub to activate the hub lock. Subsequently mechanism was developed to automatically activate the hub locks. One version (which is made part of the present invention) relies on cam actuation whereby a cam mechanism is powered by the rotation of the axles. With the propeller shaft disengaged at the transfer case, the wheel axles are non-rotating and the non-active cam mechanism allows the hub locks to disengage. With the propeller shaft engaged and thus the wheel axles rotated, the cam mechanism is activated to induce engagement of the hub locks.
Many four-wheel drive enthusiasts want both the convenience of automatic engagement and the security of manual engagement. A combination manual-automatic hub lock was first developed by Telford, U.S. Pat. No. 4,223,772. Other manual-automatic hub locks followed including U.S. Pat. Nos. 4,811,824 and 4,854,434.
Whereas the combination manual-automatic hub locks provide the desired result of enabling the operator to manually override the automatic system, the numerous parts involved render the device expensive to produce and maintain and the manual actuation somewhat difficult to operate. The present design requires fewer parts for more efficient production, easier manual operation and a more compact package of components for easier fit to the vehicle.